The
chemical compoundA chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
ammonium nitrate, the
nitrateIn inorganic chemistry, a nitrate is a salt of nitric acid with an ion composed of one nitrogen and three oxygen atoms . In organic chemistry the esters of nitric acid and various alcohols are called nitrates.-Chemical properties:...
of
ammoniaAmmonia is a compound of nitrogen and hydrogen with the formula NH
3. It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers...
with the chemical formula
NNitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere.Many industrially important...
HHydrogen is the chemical element with atomic number 1. It is represented by the symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H
2...
4NNitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere.Many industrially important...
OOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
3, is a white crystalline solid at room temperature and standard pressure. It is commonly used in
agricultureAgriculture is the production of food and goods through farming and forestry. Agriculture was the key development that led to the rise of human civilization, with the husbandry of domesticated animals and plants creating food surpluses that enabled the development of more densely populated and...
as a high-nitrogen
fertilizerFertilizers are chemical compounds applied to promote plant and fruit growth. Fertilizers are usually applied either through the soil or by foliar feeding...
, and it has also been used as an
oxidizing agentAn oxidizing agent can be defined as either:#a chemical compound that readily transfers oxygen atoms, or#a substance that gains electrons in a redox chemical reaction...
in explosives, including
improvised explosive deviceAn improvised explosive device is a homemade bomb constructed and deployed in ways other than in conventional military action...
s.
Ammonium nitrate is used in cold packs, as hydrating the salt is an
endothermicIn thermodynamics, the word endothermic "within-heating" describes a process or reaction that absorbs energy in the form of heat. Its etymology stems from the Greek prefix endo-, meaning “inside” and the Greek suffix –thermic, meaning “to heat”. The opposite of an endothermic process is an...
process.
The processes involved in the production of ammonium nitrate in industry, although chemically simple, are technologically challenging.
The
chemical compoundA chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
ammonium nitrate, the
nitrateIn inorganic chemistry, a nitrate is a salt of nitric acid with an ion composed of one nitrogen and three oxygen atoms . In organic chemistry the esters of nitric acid and various alcohols are called nitrates.-Chemical properties:...
of
ammoniaAmmonia is a compound of nitrogen and hydrogen with the formula NH
3. It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers...
with the chemical formula
NNitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere.Many industrially important...
HHydrogen is the chemical element with atomic number 1. It is represented by the symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H
2...
4NNitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere.Many industrially important...
OOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
3, is a white crystalline solid at room temperature and standard pressure. It is commonly used in
agricultureAgriculture is the production of food and goods through farming and forestry. Agriculture was the key development that led to the rise of human civilization, with the husbandry of domesticated animals and plants creating food surpluses that enabled the development of more densely populated and...
as a high-nitrogen
fertilizerFertilizers are chemical compounds applied to promote plant and fruit growth. Fertilizers are usually applied either through the soil or by foliar feeding...
, and it has also been used as an
oxidizing agentAn oxidizing agent can be defined as either:#a chemical compound that readily transfers oxygen atoms, or#a substance that gains electrons in a redox chemical reaction...
in explosives, including
improvised explosive deviceAn improvised explosive device is a homemade bomb constructed and deployed in ways other than in conventional military action...
s.
Ammonium nitrate is used in cold packs, as hydrating the salt is an
endothermicIn thermodynamics, the word endothermic "within-heating" describes a process or reaction that absorbs energy in the form of heat. Its etymology stems from the Greek prefix endo-, meaning “inside” and the Greek suffix –thermic, meaning “to heat”. The opposite of an endothermic process is an...
process.
Production
The processes involved in the production of ammonium nitrate in industry, although chemically simple, are technologically challenging. The
acid-base reactionAn acid-base reaction is a chemical reaction that occurs between an acid and a base. Several concepts that provide alternative definitions for the reaction mechanisms involved and their application in solving related problems exist...
of
ammoniaAmmonia is a compound of nitrogen and hydrogen with the formula NH
3. It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers...
with
nitric acidNitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure older samples tend to acquire a stronger yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as...
gives a solution of ammonium nitrate: HNO
3(aq) + NH
3(g) → NH
4NO
3(aq). For industrial production, this is done using anhydrous ammonia gas and concentrated nitric acid. This reaction is violent and very exothermic. After the solution is formed, typically at about 83% concentration, the excess water is evaporated to an ammonium nitrate (AN) content of 95% to 99.9% concentration (AN melt), depending on grade. The AN melt is then made into "prills" or small beads in a spray tower, or into granules by spraying and tumbling in a rotating drum. The prills or granules may be further dried, cooled, and then coated to prevent caking. These prills or granules are the typical AN products in commerce.
The
Haber processThe Haber process, also called the Haber–Bosch process, is the nitrogen fixation reaction of nitrogen gas and hydrogen gas, over an enriched iron catalyst, to produce ammonia. The Haber process is important because ammonia is difficult to produce on an industrial scale, and the fertilizer...
combines nitrogen and hydrogen to produce ammonia, part of which can be oxidised to
nitric acidNitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure older samples tend to acquire a stronger yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as...
and combined with the remaining ammonia to produce the nitrate. Another production method is used in the so-called
Odda processThe nitrophosphate process was a method for the industrial production of nitrogen fertilizers invented by Erling Johnson in the city of Odda, Norway around 1927....
.
Ammonium nitrate is also manufactured by amateur explosive enthusiasts by metathesis reactions:
2SO
4 + 2 NaNO
3 → Na
2SO
4 + 2 NH
4NO
3
- Ca(NO3)2 + (NH4)2SO4 → 2 NH4NO3 + CaSO4
Sodium sulfateSodium sulfate is the sodium salt of sulfuric acid. Anhydrous, it is a white crystalline solid of formula Na
2SO
4 known as the mineral thenardite; the decahydrate Na
2SO
4·10H
2O has been known as Glauber's salt or, historically, sal mirabilis...
is removed by lowering the temperature of the mixture. Since sodium sulfate is much less water-soluble than ammonium nitrate, it precipitates, and may be filtered off. For the reaction with calcium nitrate, the
calcium sulfateCalcium sulfate is a common laboratory and industrial chemical. In the form of γ-anhydrite , it is used as a desiccant. It is also used as a coagulant in products like tofu. In the natural state, unrefined calcium sulfate is a translucent, crystalline white rock...
generated is quite insoluble, even at room temperature.
Crystalline phases
Transformations of the crystal states due to changing conditions (temperature, pressure) affect the physical properties of ammonium nitrate. The following crystalline states have been identified:
| System |
Temperature (°C) |
State |
Volume Change (%) |
| - |
>169.6 |
liquid |
- |
| I |
169.6 to 125.2 |
cubic |
+2.1 |
| II |
125.2 to 84.2 |
tetragonal |
-1.3 |
| III |
84.2 to 32.3 |
α-rhombic |
+3.6 |
| IV |
32.3 to −16.8 |
β-rhombic |
−2.9 |
| V |
−16.8 |
tetragonal |
- |
The type V crystal is a quasi-
cubic-General:*cubicle, a small area set off by walls for special use, such as a place to work, to shower, or with a toilet.-Science and mathematics:*cube, a three-dimensional solid object bounded by six square faces, facets or sides, with three meeting at each vertex...
form which is related to
caesium chlorideCaesium chloride is the chemical compound with the formula CsCl. This colorless solid is an important source of caesium ions in a variety of applications...
, the nitrogens of the
nitrateIn inorganic chemistry, a nitrate is a salt of nitric acid with an ion composed of one nitrogen and three oxygen atoms . In organic chemistry the esters of nitric acid and various alcohols are called nitrates.-Chemical properties:...
s and the
ammoniumThe ammonium cation is a positively charged polyatomic cation of the chemical formula NH. It has a formula weight of 18.05 and is formed by the protonation of ammonia...
s are at the sites in a cubic array where Cs and Cl would be in the CsCl lattice. See C.S. Choi and H.J. Prask,
Acta Crystallographica B, 1983,
39, 414-420.
Disasters
Ammonium nitrate decomposes into
gasThis page is about the physical properties of gas as a state of matter. For the uses of gases, and other meanings, see Gas .A gas is one of four states of matter. Near absolute zero, a substance exists as a solid...
es including
oxygenOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
when heated (non-explosive reaction); however, ammonium nitrate can be induced to decompose explosively by detonation. Large stockpiles of the material can be a major fire risk due to their supporting oxidation, and may also detonate, as happened in the
Texas City disasterThe Texas City Disaster of April 16, 1947, started with the mid-morning fire and detonation of approximately 2,300 tons of ammonium nitrate on board the French-registered vessel SS Grandcamp in the port at Texas City, Texas, killing at least 581 people...
of 1947, which led to major changes in the regulations for storage and handling.
There are two major classes of incidents resulting in explosions:
- In the first case, the explosion happens by the mechanism of shock to detonation transition. The initiation happens by an explosive charge going off in the mass, by the detonation of a shell thrown into the mass, or by detonation of an explosive mixture in contact with the mass. The examples are Kriewald, Morgan (present-day Sayreville, New Jersey
Sayreville is a borough located on the Raritan River, near Raritan Bay in Middlesex County, New Jersey. As of the United States 2000 Census, the borough population was 40,377.It was ranked 47th by Money Magazine for the best places to live in 2007...
) OppauThe Oppau explosion occurred on September 21 1921 when a tower silo storing 4,500 tonnes of a mixture of ammonium sulfate and ammonium nitrate fertilizer exploded at a BASF plant in Oppau, now part of Ludwigshafen, Germany, killing 500–600 people and injuring about 2,000 more.The plant began...
, TessenderloTessenderlo is a municipality located in the Belgian province of Limburg. It is where the three Belgian provinces of Limburg, Flemish Brabant and Antwerp meet at the front gate of the Averbode Abbey. The municipality Tessenderlo encompasses the villages of Tessenderlo proper, Schoot, Engsbergen,...
and Traskwood.
- In the second case, the explosion results from a fire that spreads into the ammonium nitrate itself (Texas City
The Texas City Disaster of April 16, 1947, started with the mid-morning fire and detonation of approximately 2,300 tons of ammonium nitrate on board the French-registered vessel SS Grandcamp in the port at Texas City, Texas, killing at least 581 people...
, BrestBrest is a city in the Finistère department in Brittany in north-western France.Located in a sheltered position not far from the western tip of the Breton peninsula, Brest is an important seaport and naval base. The 1999 census recorded 303,484 inhabitants of the Brest metropolitan area, while the...
, Oakdale- United States :* Oakdale, California* Oakdale, Connecticut* Oakdale, Illinois* Oakdale, Iowa* Oakdale, Louisiana* Oakdale, Dedham, Massachusetts* Oakdale, West Boylston, Massachusetts* Oakdale, Minnesota* Oakdale, Nebraska* Oakdale, New York...
), or from a mixture of ammonium nitrate with a combustible material during the fire (Repauno, Cherokee, NadadoresNadadores is a city in the northern Mexican state of Coahuila.it serves as the administrative centre for the surrounding municipality of the same name.Nadadores is located at ,in the state's central region ....
). The fire must be confined at least to a degree for successful transition from a fire to an explosion (a phenomenon known as "deflagration to detonation transition", or DDT). Pure, compact AN is stable and very difficult to initiate, and there are numerous cases when even impure AN did not explode in a fire.
Ammonium nitrate explosives were used in the
Oklahoma City bombingThe Oklahoma City bombing occurred on April 19, 1995 when American militia movement sympathizer Timothy McVeigh, with the assistance of Terry Nichols, destroyed the Alfred P. Murrah Federal Building in downtown Oklahoma City, Oklahoma...
.
Ammonium nitrate decomposes in temperatures normally well above 200°C. However the presence of impurities (organic and/or inorganic) will often reduce the temperature point when heat is being generated. Once the AN has started to decompose then a runaway reaction will normally occur as the heat of decomposition is very large. AN evolves so much heat that this runaway reaction is not normally possible to stop. This is a well-known hazard with some types of
N-P-K FertilizerFertilizers are chemical compounds applied to promote plant and fruit growth. Fertilizers are usually applied either through the soil or by foliar feeding...
s, and is responsible for the loss of several cargo ships.
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